[llvm] [LV] Teach the loop vectorizer llvm.sincos is trivially vectorizable (PR #128035)

[Benjamin Maxwell via llvm-commits]

MacDue wrote:

> Would it be possible to add a target-independent test as well?

Sure, I've just added a simple test based on the AArch64 one. 

https://github.com/llvm/llvm-project/pull/128035